Column-spanning row in GridPanel?

Column-spanning row in GridPanel?

I have a GridPanel that lists a number of "model runs". Each row shows the run name, run location and run date.

Now, each run also has a "description" which can be a longer textual description of what the run is actually about. So, for each row entry, I would like to have a second row spanning the columns, leaving more room for the textual description to show.

I could use custom cell rendering using HTML, but that would not allow me to sort on location or run date...
I've been googling around, but for now, I haven't found anything satisfying. Can anyone get me started on how to produce something like this? Or show an example that realizes this?